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Primary Retinal Detachment

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154<br />

search for compounds with heparin-like qualities on growth factors,<br />

but without the potential hemorrhagic issues. It is known that<br />

fractionation of longer chains of heparin into smaller molecular<br />

weight fragments causes loss of some of the anticoagulant activity<br />

while preserving the ECM effects.As a result, low-molecular-weight<br />

fractions of heparin with a molecular weight of 5000 or less retain<br />

their ability to catalyze the inhibition of Factor Xa, but lose their<br />

ability to directly inhibit thrombin [49]. When low-molecularweight<br />

heparin was introduced into the infusate during vitrectomy<br />

in an animal model, fibrin formation was markedly reduced without<br />

any coincident increase in intraocular hemorrhage [50]. Use of<br />

5 IU/ml of low-molecular-weight heparin in the infusate during<br />

creation of an experimental model of proliferative vitreoretinopathy<br />

reduced the rate of traction detachment from 77% to 28% at<br />

3 months [51]. These encouraging results led to the inclusion of lowmolecular-weight<br />

heparin in the infusate, along with 5-FU, which<br />

was studied in the prevention of PVR in humans [15, 42, 50, 51].<br />

In another important PVR trial, when conventional heparin<br />

(1 IU/ml) was combined with a steroid dexamethasone (5 mg/ml)<br />

in the infusate, there was a slight increase in the retinal reattachment<br />

rate compared with controls from 65% to 80% in addition to<br />

a reduction in the rate of reproliferation from 26.5% to 16%.A mild<br />

increase in the rate of hyphema and vitreous hemorrhage was<br />

seen, although it was not judged to be clinically significant [33].<br />

Summary<br />

7 Pharmacological Approaches to Improve Surgical Outcomes<br />

Pharmacological methods remain a promising potential adjunct to<br />

the successful treatment of retinal detachment. In addition to conventional<br />

strategies, including adequate pupillary dilatation, control<br />

of inflammation by anti-inflammatory agents, and intraocular<br />

pressure by ocular hypotensive agents, drugs may play a further<br />

role by inhibiting other late complications. These include proliferation<br />

and macular edema. Steroids, fluoropyrimidines, and he-

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